Click on the partition you created for Linux, that should highlight it. Now press the small minus button at the bottom of the box and then press Apply. That will remove the partition and it will change to unpartitioned space.

Next, grab the bottom of the partition line that's your OS X partition and drag it until it fills the space up to the Boot Camp partition and press Apply.

One thing you need to be aware of: You may have zonked your Boot Camp partition's ability to boot by creating that third partition for Linux. Sometimes, you'll get lucky and it will still boot. You just have to test it. Let us know if the above works for you.